Development And Distribution Of Permian Source Rocks In Micangshan Piedmont Zone

Based on field outcrops,drilling and logging geological data and oil and gas geochemical analysis data of the research area,the organic geochemistry and resource evaluation methods are used to analyze the genetic types of the natural gas and its origin,the development and distribution of the source rocks and the hydrocarbon generation intension.Besides,the resource of the source rocks in Micangshan piedmont zone has also been calculated in this paper.This study has made the following points:(1)The natural gas of Jialingjiang-Feixianguan Formation is mainly pyrolysis of dry gas from high-post mature source rocks,which is mainly composed of Wujiaping Formation and Dalong Formation in the Upper Permian.(2)There are three sets of source rocks in the research area,including Dalong Formation,Wujiaping Formation in the Upper Permian and the third member of Maokou Formation in the Lower Permian.The organic matter abundance of the source rocks in Wujiaping Formation is relatively high,followed by the Dalong Formation and Maokou Formation,while the types of kerogen is mainly type-?kerogen,except for partly type-?kerogen in Maokou Formation.(3)The thickness of the dark muddy source rocks in the Upper Permian Dalong Formation is between 0 and 49m,and the lithology of Wujiaping Formation is dominated by mudstone,with a small amount of carbonate rocks and coal and the thickness of mudstone source rocks is mainly between 10 and 40m;the lithology of the third member in Maokou Formation is mainly mudstone,and the thickness is between 0 and50m.(4)The hydrocarbon generation and resources of the Permian in Nanjiang-Tongnanba area are calculated by the organic carbon method.The total gas production of the source rocks is 21795×10~8m~3 and the total resource is 2179×10~8m~3.Compared with Yuanba and other areas,Nanjiang-Tongnanba area has the gas source conditions to form large and medium gas field.